1. Field of the Invention
This invention relates generally to methods and systems for reading optical information, and more particularly to optical information reading methods and systems for detecting an intensity of light emitted from a scanned body with light-intensity detection means by horizontal and vertical scanning, and acquiring light-intensity image data.
2. Description of the Related Art
A conventional system for reading optical information is shown in U.S. Pat. No. 6,762,840 by way of example. This system has light-intensity detection means for detecting a light intensity by receiving light that is emitted from a scanned body, and scans the entire surface of the scanned body by repeatedly moving the light-intensity detection means relatively with respect to the scanned body in a horizontal scanning direction and in a vertical scanning direction nearly perpendicular to the horizontal scanning direction, and acquires light-intensity image data of the light emitted from the scanned body, based on an output signal from the light-intensity detection means.
For example, in the biochemistry and molecular biology fields, the aforementioned optical information read system is used in fluorescence detection systems that use a fluorescence labeling body as a labeling substance, and in chemical luminescence detection systems that use a chemical luminescence labeling body as a labeling substance.
Fluorescence detection systems can evaluate gene arrangement, gene expression levels, the path and state of the metabolism, absorption, and excretion of dosed substances in experimental mice, the separation and identification, or molecular weight and characteristics of protein, by irradiating excitation light to a gel sample in which inspection substances labeled with a fluorescence labeling body are distributed, and photoelectrically reading out fluorescence that is emitted from the gel sample when struck by the excitation light.
For instance, the molecular weight of a DNA fragment can be evaluated by electrophoresis in which charged living cells in suspension or charged biological compounds (protein, etc.) in a solution are moved to a positive or negative pole under the influence of an electric field. That is, after a fluorescence labeling body is added in a solution containing a plurality of DNA fragments, the DNA fragments are electrophoresed on a gel support; or a plurality of DNA fragments are electrophoresed on a gel support that contains a fluorescence labeling body; or after a plurality of DNA fragments are electrophoresed on a gel support, this gel support is immersed in a solution containing a fluorescence labeling body. In this manner, a gel support is obtained in which DNA fragments labeled with fluorescence are distributed. By irradiating excitation light, which excites a fluorescence labeling body employed as a labeling substance, to the gel support, the light intensity of the fluorescent light emitted from the gel support is photoelectrically read out. In this manner, light-intensity image data representing the distribution of DNA fragments labeled with fluorescence are acquired. Based on the obtained light-intensity image data, a visible image is displayed on a display unit such as a CRT display unit, whereby the molecular weight of the DNA fragment is evaluated.
The scanned body can employ a membrane or a glass slide in which inspection substances labeled with a fluorescence labeling body are distributed, in addition to the aforementioned gel support.
In chemical luminescence detection systems, a chemical luminescent substrate is brought into contact with a sample in which inspection substances labeled with a chemical luminescence labeling body are distributed, and the light intensity of the chemical luminescence emitted from the chemical luminescent substrate is photoelectrically read out. In this manner, light-intensity image data representing the distribution of inspection substances labeled with the chemical luminescence labeling body can be acquired.
As one example of a scanned body from which optical information is read out by optical information read systems, there is known a storable phosphor (stimulable phosphor) in which if radiation (X-rays, α-rays, β-rays, γ-rays, electron rays, ultraviolet rays, etc.) is irradiated, part of the radiation energy is stored and thereafter, if excitation light is irradiated, photostimulated luminescence (PSL) is emitted according to the stored energy. If radiation, transmitted through a subject such as a human body, is irradiated onto a storable phosphor sheet, the radiation image information carried by the radiation can be stored in the storable phosphor sheet. By scanning the storable phosphor sheet horizontally and vertically with excitation light such as a laser beam, photostimulated luminescence is emitted according to the stored radiation image information. By photoelectrically reading out the light intensity of the photostimulated luminescence, light-intensity pixel data is acquired for each pixel of the storable phosphor sheet. Based on the light-intensity pixel data, a sheet quantity of light-intensity image data is generated (e.g., see Japanese Unexamined Patent Publication No. 2003-029361). Thereafter, the generated light-intensity image data undergoes image processing, such as a gradation process, a frequency process, etc., suitable for observation and inspection. The processed light-intensity image data is displayed as a visible image on a display unit, such as a CRT display unit, and is used for diagnosis.
In the system disclosed in the aforementioned Publication No. 2003-029361, analog signals are obtained by reading out photostimulated luminescence with a photomultiplier tube (PMT) when reading out image information. By sampling and quantizing analog signals at predetermined intervals, the light-intensity pixel data of each pixel is acquired in a predetermined pixel density.
Visible images to be displayed are used to observe the fine structures of a scanned body, so it is desirable that visible images be reproduced in higher resolution. To meet this demand, it is desirable to acquire light-intensity image data at a high pixel density from a scanned body. For that reason, the pixel density can be enhanced by shortening the cycle during which signals output from the PMT are sampled. However, there are cases where a sampling frequency is set high to the degree that the entire sampling cycle is judged by the time of processing signals obtained. In such a case, unless the above-described processing time is shortened, it is difficult to shorten the sampling cycle. In addition, the use of a system with a high signal processing speed can be the cause of an increase in cost.